简单的Rails应用程序：错误无法访问整数
我正在尝试构建一个简单的Rails应用程序。 Rails v3.2.22.5（这是一项要求）。 我用PostgreSQL运行它。 当我启动服务器但是当我尝试从数据库中读取一个简单的post时，我收到以下错误。
无法访问Integer
跟踪引导我进入下面的show方法。 更具体到第二行。 我是Rails的新手，对于如何解决这个问题一无所知。 搜索网络已经没有成功。 任何想法都会受到欢迎。
def show @post = Post.find(params[:id]) respond_to do |format| format.html # show.html.erb format.json { render json: @post } end end 完整追踪：
arel (3.0.3) lib/arel/visitors/visitor.rb:25:in `rescue in visit' arel (3.0.3) lib/arel/visitors/visitor.rb:19:in `visit' arel (3.0.3) lib/arel/visitors/to_sql.rb:241:in `visit_Arel_Nodes_Limit' arel (3.0.3) lib/arel/visitors/visitor.rb:19:in `visit' arel (3.0.3) lib/arel/visitors/to_sql.rb:123:in `visit_Arel_Nodes_SelectStatement' arel (3.0.3) lib/arel/visitors/visitor.rb:19:in `visit' arel (3.0.3) lib/arel/visitors/visitor.rb:5:in `accept' arel (3.0.3) lib/arel/visitors/to_sql.rb:19:in `accept' activerecord (3.2.22.5) lib/active_record/connection_adapters/abstract/database_statements.rb:7:in `to_sql' activerecord (3.2.22.5) lib/active_record/connection_adapters/abstract/query_cache.rb:60:in `select_all' activerecord (3.2.22.5) lib/active_record/querying.rb:38:in `block in find_by_sql' activerecord (3.2.22.5) lib/active_record/explain.rb:41:in `logging_query_plan' activerecord (3.2.22.5) lib/active_record/querying.rb:37:in `find_by_sql' activerecord (3.2.22.5) lib/active_record/relation.rb:171:in `exec_queries' activerecord (3.2.22.5) lib/active_record/relation.rb:160:in `block in to_a' activerecord (3.2.22.5) lib/active_record/explain.rb:34:in `logging_query_plan' activerecord (3.2.22.5) lib/active_record/relation.rb:159:in `to_a' activerecord (3.2.22.5) lib/active_record/relation/finder_methods.rb:381:in `find_first' activerecord (3.2.22.5) lib/active_record/relation/finder_methods.rb:122:in `first' app/controllers/posts_controller.rb:16:in `show' actionpack (3.2.22.5) lib/action_controller/metal/implicit_render.rb:4:in `send_action' actionpack (3.2.22.5) lib/abstract_controller/base.rb:167:in `process_action' actionpack (3.2.22.5) lib/action_controller/metal/rendering.rb:10:in `process_action' actionpack (3.2.22.5) lib/abstract_controller/callbacks.rb:18:in `block in process_action' activesupport (3.2.22.5) lib/active_support/callbacks.rb:414:in `_run__2562463311931153568__process_action__1655262725222060869__callbacks' activesupport (3.2.22.5) lib/active_support/callbacks.rb:405:in `__run_callback' activesupport (3.2.22.5) lib/active_support/callbacks.rb:385:in `_run_process_action_callbacks' activesupport (3.2.22.5) lib/active_support/callbacks.rb:81:in `run_callbacks' actionpack (3.2.22.5) lib/abstract_controller/callbacks.rb:17:in `process_action' actionpack (3.2.22.5) lib/action_controller/metal/rescue.rb:29:in `process_action' actionpack (3.2.22.5) lib/action_controller/metal/instrumentation.rb:30:in `block in process_action' activesupport (3.2.22.5) lib/active_support/notifications.rb:123:in `block in instrument' activesupport (3.2.22.5) lib/active_support/notifications/instrumenter.rb:20:in `instrument' activesupport (3.2.22.5) lib/active_support/notifications.rb:123:in `instrument' actionpack (3.2.22.5) lib/action_controller/metal/instrumentation.rb:29:in `process_action' actionpack (3.2.22.5) lib/action_controller/metal/params_wrapper.rb:207:in `process_action' activerecord (3.2.22.5) lib/active_record/railties/controller_runtime.rb:18:in `process_action' actionpack (3.2.22.5) lib/abstract_controller/base.rb:121:in `process' actionpack (3.2.22.5) lib/abstract_controller/rendering.rb:46:in `process' actionpack (3.2.22.5) lib/action_controller/metal.rb:203:in `dispatch' actionpack (3.2.22.5) lib/action_controller/metal/rack_delegation.rb:14:in `dispatch' actionpack (3.2.22.5) lib/action_controller/metal.rb:246:in `block in action' actionpack (3.2.22.5) lib/action_dispatch/routing/route_set.rb:73:in `dispatch' actionpack (3.2.22.5) lib/action_dispatch/routing/route_set.rb:36:in `call' journey (1.0.4) lib/journey/router.rb:68:in `block in call' journey (1.0.4) lib/journey/router.rb:56:in `each' journey (1.0.4) lib/journey/router.rb:56:in `call' actionpack (3.2.22.5) lib/action_dispatch/routing/route_set.rb:608:in `call' actionpack (3.2.22.5) lib/action_dispatch/middleware/best_standards_support.rb:17:in `call' rack (1.4.7) lib/rack/etag.rb:23:in `call' rack (1.4.7) lib/rack/conditionalget.rb:25:in `call' actionpack (3.2.22.5) lib/action_dispatch/middleware/head.rb:14:in `call' actionpack (3.2.22.5) lib/action_dispatch/middleware/params_parser.rb:21:in `call' actionpack (3.2.22.5) lib/action_dispatch/middleware/flash.rb:242:in `call' rack (1.4.7) lib/rack/session/abstract/id.rb:210:in `context' rack (1.4.7) lib/rack/session/abstract/id.rb:205:in `call' actionpack (3.2.22.5) lib/action_dispatch/middleware/cookies.rb:341:in `call' activerecord (3.2.22.5) lib/active_record/query_cache.rb:64:in `call' activerecord (3.2.22.5) lib/active_record/connection_adapters/abstract/connection_pool.rb:479:in `call' actionpack (3.2.22.5) lib/action_dispatch/middleware/callbacks.rb:28:in `block in call' activesupport (3.2.22.5) lib/active_support/callbacks.rb:405:in `_run__2325253408966325104__call__3112622970942194936__callbacks' activesupport (3.2.22.5) lib/active_support/callbacks.rb:405:in `__run_callback' activesupport (3.2.22.5) lib/active_support/callbacks.rb:385:in `_run_call_callbacks' activesupport (3.2.22.5) lib/active_support/callbacks.rb:81:in `run_callbacks' actionpack (3.2.22.5) lib/action_dispatch/middleware/callbacks.rb:27:in `call' actionpack (3.2.22.5) lib/action_dispatch/middleware/reloader.rb:65:in `call' actionpack (3.2.22.5) lib/action_dispatch/middleware/remote_ip.rb:31:in `call' actionpack (3.2.22.5) lib/action_dispatch/middleware/debug_exceptions.rb:16:in `call' actionpack (3.2.22.5) lib/action_dispatch/middleware/show_exceptions.rb:56:in `call' railties (3.2.22.5) lib/rails/rack/logger.rb:32:in `call_app' railties (3.2.22.5) lib/rails/rack/logger.rb:16:in `block in call' activesupport (3.2.22.5) lib/active_support/tagged_logging.rb:22:in `tagged' railties (3.2.22.5) lib/rails/rack/logger.rb:16:in `call' actionpack (3.2.22.5) lib/action_dispatch/middleware/request_id.rb:22:in `call' rack (1.4.7) lib/rack/methodoverride.rb:21:in `call' rack (1.4.7) lib/rack/runtime.rb:17:in `call' activesupport (3.2.22.5) lib/active_support/cache/strategy/local_cache.rb:72:in `call' rack (1.4.7) lib/rack/lock.rb:15:in `call' actionpack (3.2.22.5) lib/action_dispatch/middleware/static.rb:83:in `call' railties (3.2.22.5) lib/rails/engine.rb:484:in `call' railties (3.2.22.5) lib/rails/application.rb:231:in `call' rack (1.4.7) lib/rack/content_length.rb:14:in `call' railties (3.2.22.5) lib/rails/rack/log_tailer.rb:17:in `call' rack (1.4.7) lib/rack/handler/webrick.rb:59:in `service' /Users/luishreis/.rbenv/versions/2.4.1/lib/ruby/2.4.0/webrick/httpserver.rb:140:in `service' /Users/luishreis/.rbenv/versions/2.4.1/lib/ruby/2.4.0/webrick/httpserver.rb:96:in `run' /Users/luishreis/.rbenv/versions/2.4.1/lib/ruby/2.4.0/webrick/server.rb:290:in `block in start_thread'
您正在使用的Ruby版本（2.4.1）与您正在使用的Rails版本（3.2.22.5）不兼容。 该版本的Ruby至少需要Rails 5.尝试降级到Ruby 2.3或更低版本。 您可以使用Ruby版本管理器（即rvm ， rbenv或chruby ）来控制启动应用程序时使用的Ruby。
编辑
刚刚注意到你已经在堆栈跟踪中使用了rbenv 。 将.ruby-version文件添加到包含以下行的应用程序目录中：
2.3.4
重新进入该目录后，通过以下方式确认版本：
$> ruby -v ruby 2.3.4p301 (2017-03-30 revision 58214) [x86_64-darwin16]
（或类似版本）在启动rails之前。
我昨天得到了这个错误并创建了一个解决方法，它应该可以使用ruby 2.4和rails 3.2。
我从中得到的想法是： https ： //github.com/rails/arel/commit/dc85a6e9c74942945ad696f5da4d82490a85b865
只需在rails初始化程序中包含以下内容即可。
module Arel module Visitors class DepthFirst < Arel::Visitors::Visitor alias :visit_Integer :terminal end class Dot < Arel::Visitors::Visitor alias :visit_Integer :visit_String end class ToSql < Arel::Visitors::Visitor alias :visit_Integer :literal end end end
对于未来的Google员工。 我有同样的问题，但我需要应用Thomas Dziedzic解决方案的变体。
我的系统中运行了ruby 2.5.1和rails 4.2.10 。
如此提交中所示，ToSql已从Arel::Visitors::Visitor更改为Arel::Visitors::Reduce
所以这是我更新的解决方案。 在rails初始化程序中输入：
module Arel module Visitors class DepthFirst < Arel::Visitors::Visitor alias :visit_Integer :terminal end class Dot < Arel::Visitors::Visitor alias :visit_Integer :visit_String end class ToSql < Arel::Visitors::Reduce alias :visit_Integer :literal end end end